A232155 Number of n X 2 0..3 arrays with every 0 next to a 1, every 1 next to a 2 and every 2 next to a 3 horizontally, vertically or antidiagonally, and no adjacent values equal.

2, 18, 62, 218, 746, 2600, 9004, 31262, 108492, 376566, 1307146, 4537292, 15750222, 54673186, 189786782, 658806476, 2286917482, 7938591212, 27557292770, 95659868830, 332064969492, 1152700237642, 4001379292082, 13890026339060

Offset: 1

Author

R. H. Hardin, Nov 19 2013

Keywords

• nonn

Examples

			Some solutions for n=7:
..2..1....2..3....3..1....0..3....1..3....0..1....0..1....2..1....3..0....1..2
..3..0....0..1....0..2....1..2....2..1....2..3....3..2....3..2....1..3....0..3
..2..3....2..3....3..1....3..0....3..0....1..2....0..1....1..0....2..0....1..0
..1..2....0..1....2..0....2..1....1..2....0..3....3..2....3..2....1..3....2..1
..3..1....2..3....3..1....3..2....3..1....1..0....1..3....0..1....2..1....3..0
..2..0....1..2....0..2....1..0....2..3....2..3....2..1....3..2....3..0....1..2
..3..2....0..3....1..3....2..3....1..0....1..2....3..2....0..1....2..1....3..1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Column 2 of A232161.

Formula

Empirical: a(n) = 4*a(n-1) + 2*a(n-2) - 13*a(n-3) - 5*a(n-4) + 14*a(n-5) - 3*a(n-6) + 3*a(n-7) + 8*a(n-8) + a(n-9) - a(n-10) for n>11.

Empirical g.f.: 2*x*(1 + 5*x - 7*x^2 - 20*x^3 - 3*x^4 + 24*x^5 + 5*x^6 + 7*x^7 + 15*x^8 + 2*x^9 - 2*x^10) / (1 - 4*x - 2*x^2 + 13*x^3 + 5*x^4 - 14*x^5 + 3*x^6 - 3*x^7 - 8*x^8 - x^9 + x^10). - Colin Barker, Oct 03 2018